Plate cylinder for wrap-around printing plate and method



3,126,825 METHOD March 31, 1964 F. J. TOFANO PLATE CYLINDER FOR WRAP-AROUND PRINTING PLATE AND OF CONVERTING SAME FROM CYLINDER EQUIPPED TO CARRY THICKER PRINTING PLATES 2 Sheets-Sheet 1 Filed Aug. 2, 1962 I v PDOKMQ 2D I OmN O l lllll I illilllll:Ii filliil null N r. Lu T .l Hfi .54. 1 )Pflv r l 0mm- I II T Hm I mmw I 5 1 ab: m. w 25.; 0 w w 6 a W l H u 3| iii! II I I fimwv mwmw fiwvw R R R x BMW I fi wn" 1? H ||ili 1. "1. 9 r rhf- Q 1i N it s a R Y m w mm m mm W m A 5 s m m Q March 31, 1964 F. J. TOFANO 3,126,825

PLATE CYLINDER FOR WRAP-AROUND PRINTING PLATE AND METHOD OF CONVERTING SAME FROM CYLINDER EQUIPPED T0 CARRY THICKER PRINTING PLATES Filed Aug. 2, 1962 2 Sheets-Sheet 2 INVENTOR. FRANK J. TOFANO M EWMI his A TTORNEYS.

United States Patent 3,126,825 PLATE CYLINDER FGR WRAP-AROUND PRINT- [NG PLATE AND METHOD OF CONVERTING SAME FROM CYLINDER EQUIPPED TO CARRY TIHCKER PRDITING PLATES Frank J. Tofano, Bronx, N.Y., assignor to Dun & Bradstreet, Inc., New York, N.Y., a corporation of Dela- Ware Filed Aug. 2, 1962, Ser. No. 214,273 9 Claims. (Cl. 101-415.1)

This invention relates to a novel printing plate cylinder for Wrap-around printing plates and to a novel method of converting a plate cylinder equipped to carry thicker printing plates, such as electrotype, stereotype and rotogravure plates, to a plate cylinder equipped to carry thinner printing plates of the wrap-around type, such as planographic and relief Wrap-around plates.

In certain plate-carrying cylinders used in printing presses, especially cylinders designed for letterpress printing, the plates are mounted against a recessed or undercut plate-receiving surface. To convert such platecarrying cylinders to a cylinder capable of receiving a wrap-around lithographic plate, it has been the practice to build up the plate-receiving surface by electroplating or spraying an excess thickness of metal thereon, and then machining the surface to remove the excess metal, thereby producing a uniform plate-receiving surface of proper depth for the wrap-around plate. Needless to say, such conversion is both costly and burdensome, and once the conversion is made, reconversion back to a letterpress cylinder is not practicable.

The present invention provides a novel plate cylinder converted from one equipped to carry thicker plates to one equipped to carry thinner wrap-around plates. Toward this end, the novel plate-carrying cylinder has a recessed plate-receiving surface, a continuous underlay of uniform thickness made of flexible, relatively non resilient and uncompressible sheet material wrapped around and anchored to the plate-receiving surface, the opposite edges of the underlay leaving a gap therebetween which extends lengthwise of the cylinder, and a clamp accommodated within the gap to grip the opposite edges of a plate wrapped around the underlay and to hold the plate to the cylinder. In this cylinder assembly, the underlay not only provides a continuous, uniform backing for the wrap-around plate, but it is of the necessary thickness to compensate for the differences in the thicknesses of the plates, so that in operation the wrap-around plate will engage the impression surface of the printing couple with the necessary pressure to form clearly printed impressions. In this connection, it is particularly critical that the underlay sheet does not tend to compress as it passes through the bite between the cylinders forming the printing couple.

The present invention also provides a simple, inexpensive method of converting the above-described printing cylinder from one which carries thicker printing plates to one which carries a thinner map-around plate. This method includes the steps of removing any plate clamps and other detachable hardware from the section of the recessed surface to receive the wrap-around plate, filling any voids of significant size in the recessed surface with relatively rigid inserts or uncompressible material to produce a uniform cylindrical surface, wrapping and anchoring a flexible, relatively non-resilient and uncompressible sheet of the desired uniform thickness around the recessed surface except for a gap between opposite ends thereof, and equipping the cylinder with a clamp for gripping opposite edges of a plate wrapped around the underlay sheet, the clamp being accommodated within the gap defined between the opposite edges of the underlay. The

3,126,825 Patented Mar. 31, 1964 underlay sheet can be fastened directly to the recessed surface of the cylinder by tapping holes and inserting screws where necessary, but preferably, it is secured to transverse void-filling inserts which extend the length of the section of the cylinder to receive the wrap-around plate.

There are a number of distinct advantages to the present invention. First of all, the material and labor costs involved in converting the press are greatly reduced in comparison to methods in which metal is deposited over the entire area of the plate-receiving surface and then removed to produce a surface of uniform diameter. Also, the equipment needed to make the transformation is simple and inexpensive. Secondly, the cylinder can be reconverted, if desired, to receive the thicker plates by removing the filler blocks, plate clamp and filler sheets and replacing the original hardware. As pointed out above, reconversion is difiicult, if not impossible, when the original conversion is made by building up metal on the plate-receiving surface. Thirdly, the present invention makes it possible to use a single press for both planographic and letterpress methods of printing, since the conversion from one to the other is quickly and easily made.

For a more complete understanding of the present invention, reference can be made to the detailed description which follows, and to the accompanying drawings, in which:

FIGURE 1 is a view partly in cross-section, with a large intermediate section broken away, of a typical plate cylinder converted from one adapted to receive a letterpress plate to one capable of receiving a planographic plate;

FIGURE 2 is a sectional view of the cylinder taken along the line 2--2 of FIGURE 1; and

FIGURE 3 is a composite view showing sectional views of the plate cylinder, the flexible underlay and the wraparound printing plate to be carried by the cylinder.

Referring to FIGURE 1, the plate cylinder 10 converted according to the present invention is equipped with axles 12 which are adapted to be journaled in a frame 13 of the printing press. The plate cylinder shown is of a type designed to carry sixteen letterpress plates before the conversion, four quadrants each accommodating four plates in side-by-side relation. After conversion, as shown in FIGURE 1, the plate cylinder is equipped to carry two wrap-around lithographic printing plates 34 in side-by-side relation. It is, of course, understood that the number of printing plates carried by the cylinder before and after conversion is immaterial as far as the present invention is concerned.

The plate cylinder has an outer recessed or under-cut cylindrical surface 14 which extends substantially over the entire length of the cylinder between a pair of end rims 15 which are of substantially larger diameter than the plate-carrying surface 14. Before conversion, the plate cylinder carried a plurality of plate clamps 16 which served to lock the letterpress plates against the platecarrying surface 14. However, in the converted cylinder shown in FIGURE 1, all of the plate clamps have been removed, except a group at each end of the cylinder just inside the inner surfaces of the rims 15 which are equally spaced apart around the periphery of the cylinder out of the way of the portion of the cylinder which is to be used for carrying the wrap-around printing plates. These plate clamps are slidably accommodated within slots 18 recessed in the plate cylinder. The closures 20 cover enlarged openings in the slots 18 through which the inner portions of the plate clamps can be removed. The plate clamps which are shown serve no useful purpose in the converted cylinder, and they have been retained only S because they are out of the Way and by leaving them the job of reconverting the cylinder for letterpress printing is made that much easier.

The plate-carrying surface 14 has four channel-like grooves or recesses 22 spaced at 90 intervals, each extending substantially the length of the cylinder. These channels serve to receive flanges on the ends of the letterpress plates. A ring 23 is mounted at the center of the cylinder, but it serves no useful purpose in the converted cylinder; nevertheless, it need not be stripped off the cylinder because it does not interfere with the conver- SlOIl.

In converting the plate cylinder for lithographic printing, the section of the plate-carrying surface on which the wrap-around plate is to be mounted is stripped of all projecting hardware, such as the plate clamps 1d. Since the surface must be free from voids and realtively rigid, any voids left by the removal of the projecting hardware must be filled with rigid inserts, such as wooden or metal blocks, or some material that will not compress as it passes through the bite of the printing couple. In this connection, rigid inserts 24 are placed and anchored in three of the longitudinal channels 22 by means of flatheaded screws 26 inserted in holes which have been tapped in the plate cylinder. These inserts completely fill the respective channels and have outer surfaces which conform to the surface 14. Wood has been found to be advantageous for these inserts because it is easily shaped and the screw holes can be readily formed therein.

Two flexible underlay or filler sheets 28 of suitable length, width and thickness are then wrapped about the surface 14 and secured to the inserts 24 by means of screws 30. adapted for use as the underlay since it has the necessary characteristics of flexibility and uncompressibility and it is easily cut to the desired size. Rubber, on the other hand, is entirely too resilient, causing uneven definition of the print. In the particular plate cylinder assembly shown in FIGURE 1 of the drawing, one of the underlay sheets is installed on each side of the ring 23, the widths of each extending from the ring to the inner edges of the respective set of plate clamps 16. It is apparent that the ring 23 could have been removed and a single underlay sheet used instead. However, a single sheet is more cumbersome and difiicult to install.

The length of each of the underlay sheets 28 is such that its opposite edges are spaced apart to define a gap Polyethylene has been found to be best which exposes the remaining channel 22. This channel accommodates a plate clamp therein for mounting the wraparound printing plate 34 on the cylinder. The plate clamp can take various forms, but in the embodiment shown in the drawings, it includes a lower base strip or insert 36 affixed therein by screws 37 and an outer plateclamping strip 38 which is detachably secured to the base strip by screws 40. The ends of the printing plate are bent around the edges of the underlay sheet and are gripped between the base strip and the clamping strip, so that a slight clearance must be provided between the edges of the underlay sheet and the plate-clamping strip to accommodate these bent ends of the printing plate.

The lower base strip is preferably recessed within the channel 22 and the outer surface of the plate-clamping strip recessed slightly within the circumference of the outer surface of the plate. This serves not only to keep the plate clamp out of contact with the paper to be printed, but if the paper is a web it serves to relieve tension on the paper web during each revolution of the cylinder.

The underlay sheet can be installed in any suitable manner. One method is to pre-cut a polyethylene sheet of the desired thickness to the necessary size and wrap the sheet around the surface 14. After lining up the edges of the sheet with the plate clamp 36, the sheet can be held in place by connecting the edges with strips of pressure-sensitive adhesive tape which span the plate 4 clamp. Starting some distance from. the leading edge of the underlay sheet, a row of threaded holes is drilled through the polyethylene sheet and into the cylinder, preferably at the places where the underlay sheet is backed by the wooden inserts 24. If it is attempted to begin by anchoring the leading edge of the underlay sheet to the cylinder it may result in a wavy condition in the sheet. The fiat-headed screws 30 which are inserted should be slightly recessed below the surface of the underlay sheet and polyethylene molded over the screw heads. The cylinder can then be placed under normal pressure and the cylinder inched from the leading edge toward the trailing edge of the underlay sheet to iron out the sheet, and the cylinder can be stopped to place more screws as may be desired. Since it has been found advantageous to leave the leading and trailing ends unattached, the screws 3t can, if desired, be restricted to the areas where the underlay sheet is backed by the wooden inserts 24. The unattached leading and trailing ends of the underlay sheet will be held tightly against the cylinder during operation by the tightly clamped wrap-around plate 34.

The thickness of the underlay sheet depends on the amount which the recessed surface 14 must be built up to compensate for the difference in thickness between the different types of printing plates. FIGURE 3 shows, for example, a printing plate having a thickness of 0.015 inch to be applied to a cylinder having an undercut of 0.250 inch. Accordingly, the proper thickness for the underlay sheet in 0.235 inch. Incidentally, the exact thickness of an underlay sheet cannot be obtained, one thinner than the desired thickness by about several thousandths of an inch can be used and the difference made up by wrapping the cylinder with a sheet of heavy paper before the underlay sheet is applied.

The invention has been shown and described in a single form and by way of example, and obviously, many modifications and variations can be made therein witmn the spirit of the invention. The foregoing description, therefore, should be considered merely as illustrating one example of the invention, and not as limiting the appended claims.

I claim:

1. A printing plate cylinder converter from one equipped to carry relatively thick plates to one equipped to carry a thinner wrap-around plate comprising a recessed cylindrical plate-carrying surface, a continuous underlay of uniform thickness made of flexible, relatively uncompressible sheet material wrapped around the platecarrying surface, the opposite edges of the underlay sheet being spaced apart to leave a longitudinally extending gap between, a plurality of longitudinally extending recesses in said plate-carrying surface spaced apart from each other around the cylinder beneath said underlay sheet, rigid inserts filling and anchored within said longitudinally extending recesses, said rigid inserts having outer surfaces curved to the same circumference as the platecarrying surface, and plate-clamping means carried by the cylinder within the gap to grip opposite edges of a plate wrapped around the underlay sheet.

2. A printing plate cylinder as set forth in claim 1 in which the plate-clamping means is accommodated within one of said longitudinally extending recesses.

3. A printing plate cylinder as set forth in claim 1 in which the underlay sheet is polyethylene.

4. A printing plate cylinder as set forth in claim 1 .in which the rigid inserts are wood.

5. A printing plate cylinder as set forth in claim 1 in which the ends of the underlay sheet are unattached to the cylinder.

6. A method of converting a printing plate cylinder from one which carries thicker printing plates to one which carries a thinner wrap-around printing plate, said cylinder having a cylindrical plate-receiving surface which contains a plurality of longitudinally extending recesses spaced apart around the cylinder, the method comprising 6 filling the recesses which the plate will overlie with a 7. A method as set forth in claim 6 in which the underrelatively uncompressible material having an outer SUI- lay sheet is polyethylene. face of the same circumference as the plate-carrying 8. A method as set forth in claim 6 in Which the surface, Wrapping a flexible, relatively uncompressible fillers are rigid Wooden inserts.

underlay sheet around the cylindrical surface, leaving a 5 9. A method as set forth in claim 6 in which the ends gap between opposite edges of the underlay sheet, said gap of the underlay sheet are left unattached to the cylinder. including one of the longitudinally extending recesses,

anchoring the underlay sheet to the fillers, and equipping References Cited in the file Of this Patent the recess within said gap with plate-clamping means for UNITED STATES PATENTS clamping opposite edges of the wrap-around printing 10 2 730 949 Mitchell Jan 17 1956 plate. 

1. A PRINTING PLATE CYLINDER CONVERTER FROM ONE EQUIPPED TO CARRY RELATIVELY THICK PLATES TO ONE EQUIPPED TO CARRY A THINNER WRAP-AROUND PLATE COMPRISING A RECESSED CYLINDRICAL PLATE-CARRYING SURFACE, A CONTINUOUS UNDERLAY OF UNIFORM THICKNESS MADE OF FLEXIBLE, RELATIVELY UNCOMPRESSIBLE SHEET MATERIAL WRAPPED AROUND THE PLATECARRYING SURFACE, THE OPPOSITE EDGES OF THE UNDERLAY SHEET BEING SPACED APART OT LEAVE A LONGITUDINALLY EXTENDING GAP BETWEEN, A PLURALITY OF LONGITUDINALLY EXTENDING RECESSES IN SAID PLATE-CARRYING SURFACE SPACED APART FROM EACH OTHER AROUND THE CYLINDER BENEATH SAID UNDERLAY SHEET, RIGID INSERTS FILLING AND ANCHORED WITHIN SAID LONGITUDINALLY EXTENDING RECESSES, SAID RIGID INSERTS HAVING OUTER SURFACES CURVED TO THE SAME CIRCUMFERENCE AS THE PLATECARRYING SURFACE, AND PLATE-CLAMPING MEANS CARRIED BY THE CYLINDER WITHIN THE GAP TO GRIP OPPOSITE EDGES OF A PLATE WRAPPED AROUND THE UNDERLAY SHEET. 